Shock-absorbing motion accelerator



Feb. 23 1926. 1,573,818

5. EINSTEIN ET AL SHOCK ABSORBING MOTION ACCELERATOR Filed Oct. 25, 1925 I5 Sheets-Sheet 1 WM R S. EINSTEIN ET AL SHOCK ABSORBING MOTION ACCELERATOR Filed Oct. 25, 1923 3 Sheets-Sheet 2 Feb. 23 1926.

. mum

v my:

OZ 1 Jwuewfozp 35 w Feb- 23 1926. S. EINSTElN ET AL snocx ABSORBING MOTION ACCELERATOR 1923 3 Sheets-Sheet :5

Filed Oct. 25

' Qu will:

kw m Ill] Patented Feb. 23, 1926 UNITED STATES PATENT.OFFICE.

SOL EINSTEIN, OF CINCINNATI, AND HER-MAN R. ISLER, OF NOBWOOD, OHIO, AS- SIGNORS, BY MESNE ASSIGNMENTS, TO THE TCINCINNATI MILLING MACHINE COM- PANY, OF CINCINNATI, OHIO, A CORPORATION OF OHIO.

SHOCK-ABSORBIN G MOTION ACCELERATOR.

Application filed October 25, 1923. Serial Ho. 670,774.

7 '0 all wlz am it may concern Be it known that we, SoL EINSTEIN and HERMAN R. ISLER, each a citizen of the United States, and residing at Cincinnati and Norwood, respectively, in the county of Hamilton and State of Ohio, have invented a new and Improved Shock-Absorbing Motion Accelerator, of which the following specification is a full disclosure.

This joint invention is directed to the proposition of accomplishing the speeding up of a work-carrier, as in a machine-tool, in

a manner such that the inertia will be overcome so gradually that no jolts or undue vibrations be created. The normal rate of travel of the reciprocating table of a grinding-machine is usually such that, if its propelling mechanism he suddenly clutched in a reverse way to the power-driven transmission, the momentum of the parts and the rapidly running gears of the transmission will exercise a hammer-like action on the table and create vibrations detrimental to the finish of the ground surface.

This joint invention, however, proposes transmission may be caused to bring the table from a dead-stop to its normal rate of travel quickly and positively yet not so abruptly as to produce vibrations or jars.

On the other hand, when the normal rate of travel is moderate, the reversal, if accomplished without, the aid of any shockabsorbing-instrumentality, will not give rise to undue jars, and this invention accordingly proposes that an arrangement such that said instru-Inentality may be rendered idle when not needed so that the reversal may be accomplished more expeditiously and directly. Thus, the combination embodies a gradual motion accelerator which may, or may not, be resorted to by the mere setting of an appropriate hand-lever, or the like to meet the varied conditions of service of the grindingmachine. Y

Another object is to render available a sub-mechanism capable of functioning to accelerate the speed in a resilient manner so as impositively to propel the table until the inertia'has been overcome and the normal speed has thus been smoothly attained, and then to carry on the propulsion through a positive drive up to the next station of reversal,

A further object is to devise a smoothly- I acting motion accelerator that will be structurally simple, composed of but few elements, and of a durable character and capable of long usage without adjustment or repair, and which shall be ver compact and easily capable of being com ined with the other transmission members.

Other objects and advantages will be in part indicated in the following description and in part rendered apparent therefrom in connection with the annexed drawings.

To enable others skilled in the art so fully to apprehend the underlying features hereof that they may embody the same in the various ways contemplated by thisin- I vention, drawings depicting a preferred typical construction have been annexed as a part of this disclosure and, in such drawings, like characters of reference denote corresponding parts throughout all the views, of which i Fig. 1 is a fragmentary plan partly in section showing the details of the lever for reversing the traverse of the table and of the means for effecting a soft reversal. Fig. 2 is a fragmentary front-elevation, partly in section, showing said lever and also further details of the load-andfire mechanism which is a part of the soft reversal means. Fig. 3 is a vertical section through line 13--13 of Fig. 2 showing further details of the reversing lever and of the soft reversal mechanism. Fig, 4 is a horizontal section showing the reversing clutch, the load-andfire actuator therefor, and the clutch for operating the soft reversal mechanism; Fig. 5 is a section through line 15-15 of Fig. 1 showing further details of the means for causing the soft action mechanism to function. Fig. 6 is a vertical section through line 6-6 of Fig. 8 showing the rack and pinion for traversing the table and showing the clutch whereby the power traverse may be disconnected to enable the traverse to nection with the transmission leading from.

be traversedby hand. i

The transmission to the saddle derives motion from a shaft 3 located at the left side of the machine and extending upwardly and forwardly to connect with a bevel gear 3 journal ed in a swivel casting 27 which is mounted to rock in the end of the saddle, as shown best by Fig. 8. The purpose of the swivel casting 27 is to accommodate the in-and-out feeds of the saddle. A mainpower shaft 3* extends longitudinally through the saddle from one end to the other, as shown best by Fig. 8 and is preferably journaled at appropriate points 28 therein.

The table-feed transmission comprises the train 3, 8 .8", 8, 8., 8,8, 8 and 8 leading to the soft motion accelerator including the elements 9, 9", 9, 9, 9, 1, 1, 1, 1 and the train therefrom comprising the elements 2 2", 2, 2 2, 2 and the train (operative selectively by hand or power) 3, 3, 3, 3, and the rack 3 secured to the under-side of the table, The change-gears primarily controlling the rate of motion ofthe tablefeed transmission are shown best by Figs. 3, 5, 8 and 9 and include a 3-gear unit 77 splined on the shaft 3 and shiftable to mesh with the matching-gears of the intermediate 3- gear unit 78 journaled on shaft 79. A shiftable 2-gear unit 8 is splined to shaft 8 and may, by suitable means, be meshed with any one of the two matching-gearson, the intermediate unit 78. Keyed to the shaft 8 and running as a unit therewith is a gear 8 which permanently drives a gear 8 keyed to an elongated sleeve journaled on the shaft 7 9 and having at its right-hand end (Fig. 8)

a' gear 8 which permanently meshes with a free-running gear 8 which provides a ratchet connection with a member 1 keyed to the shaft 1 on which the shiftable motion reversingclutch-collar 1 is splined. It will be noted that'the gears 8, 8, and 8 and 8 are proportionatein a speed reduction ratio so that the gear 8 always runs considerablyv slower thanthe gear 8. It may transmit this relatively slow rotation to the member 1 through the aforesaid ratchet mechanism which is shown in detail by 7 and comprises a pawl 8. This permits the shaft 1 when otherwise appropriately driven, to rotate at a greater speed'than the gear 8 owing to'th capement of the pawl,8 over the "the ratchet mechanism when said being driven faster than the push and. YVhen, at the reversal, the

table is being started from a stop position,

the aforesaid mechanism is advanced under ,the table up to its full rate of travel, so as to avoid the shock which would otherwise cause vibration in the machine. This speed accelerator is so constructed as to gradually attain the full rate of speed and it comprises a sleeve 9* rotatable and translatably mounted on the sleeve 8 and connected to the gear-unit 8' by means of acoarse pitch thread 85. An expansile coil spring 86 is enclosed by the sleeve 9" and is adequate normally to push the sleeve 9* to the right from the gear-unit 8 into the position shown by Fig. 8., When the clutch-collar 1 is disengaged from the clutch-teeth 9 of the gearunit 9 which is loosely journaled on the shaft 8 and is geared to the gear teeth 9 formed on the sleeve 9". Normally, the parts 8", 9", and 9 rotate freely (with the sleeve in its extreme right-hand position) but assoon as the collar 1 is clutched to the gear-unit 9 the latter (which normally runs considerably faster) is caused to rotate as a unit with the clutch 1 and the shaft 1' and so on up to the table. In other words, the gear-unit 8' is now caused to rotate faster than the sleeve 9 with the result that the sleeve is screwed to'the left by the relative motion against the pressure of the spring 86 until the force transmitted is sufficient to cause the gear unit 9 to drive the clutch-unit collar 1 instead of being driven by the latter. The spring now has become an agent in the transmission of motion to the table and being resilient and, since it continues to be screwed tothe left to increase the pressure of the spring, the motion is transmitted at a progressively increased rate until finally the clutch-teeth 9 on the left-hand end of the sleeve 9" will engage the clutch-teeth 87 projecting from the face of the gear 8 whereupon the drive becomes positive at the normal high rate of travel of the table determined by the change-gears. Conversely, when the clutch collar 1 is disengaged, the gear 9 is free to spin without restriction and the spring 86 thereuponrestores the sleeve 9 to its position shown by Fig. 8 thus enabling the travel of the table to be slowed down by friction smoothly to the rate determined by the slower rotating gear 8. It has been found by practice that this mechanism operates very smoothly as a table accelerator so that the latter may be reversed in its direction of travel etc. without perceptible shock. v

The reversal in the direction of travel is achieved by shifting the collar l to make either of the two bevels 2 and 2 the driver for .the bevel-gear 2 which is keyed to a shaftz} that carries the worm 2 meshing with 'a worm-wheel. 2 loosely journaled on a vertical shaft 88. On its upperend, the gear 3' is loosely journaled. also on the shaft 88 and permanently meshes with the rack 3 whiclnpropels the table. When it is desired that the table shall be fed by power, a clutch 3" (which through the teeth 3 is splined to the gear 3) is shifted into engagement with the worm-wheel 2 so as' to be driven thereby and in turn drive the gear 3'. Conversely, when it is desired to advance the table by hand, this clutch is disconnected and the gear 3' may be. rotated by means now briefly to be described. A lever 4 (of which there may be duplicates on the machine as shown) isadapted, upon a suitable movement to be operatively connected with a shaft 4 (see Figs. '2, 6 and 8) which carries agear 3 in mesh with'a gear 3 integral with the gear 3f. Thus by first swinging the lever 4 in the direction of the length of the shaft 4 to connect cer' tain clutch elements (not shown) and then swinging it about the axis of the shaft 4 the gear 3 may be rotated and the table be translated manually.

The manual means for reversing the table travel comprises a lever 89 also mounted on the apron of the saddle and immediately accessible to the user. This lever is pinned to a shaft 90 which extends through the apron (Fig. 3) and has depending from its inner end an arm 91 which enters a slot 92 cut-in one side of a shift-rod 93. This rod, through a species of load-and-fire device operates a clutch shifter 94 slidably mounted on a fixed shaft 95 as shown best by Fig. 4. By this means, the reversal of the table travel can be accomplished manually and the means for accomplishin it automatically utilizes these elements in combination with others as will now be explained.

The automatic table-reverse]: comprise dogs 96 appropriately secured in adjustabT: positions at the right and the left sides of the table respectively by means of the usual T-slot 97 and by means of the finger-clamps 98. These-dogs have contact surfaces 99 traveling in the path of a finger 100 which may be withdrawn manually if desired and which is mounted on the reversing lever 89 as shown best by Fig. 3. VVhencthe table is traveling to the left, the contact surface 99 comes against thefinger 100 and gradually moves the lever 89 counter-clockwise which causes its lower end 91 to shift the shaft 93 towards the right. On that shaft are two catches 101 and 102 which may be moved closer together against the spring 103 but which have their separation limited by suitable shoulders 104 and 105. These catches, at their vertical sides, are adapted to engage shoulders 106 and 107 provided by the clutch-shifter 9-1 which engages the clutch-collar 1 When the shaft 93 is shifted to the right, it will be perceived that the catch 102 only is effective and when it is shifted to the left, the catch 101 only 101 and 102 is accom lished only by reason of the spring 103 an to permit that movement to be accomplished at an exact point in the travel of the lever 89, a trigger-like action is provided. For example, when the shaft 93 is moved to the right, the shoulder 104 pushes the catch 101 also to the right but the catch 102 does not immediately move; being temporarily restrained by a shoulder 114- provided on the underside of alink 115 which is pivoted at 116. The forward end of that link is provided with a bevel 117 in the path of the corresponding bevel on the catch 101 and the link remains in place by gravity until these bevels engage; whereupon the link is lifted by the catch 101 and the catch 102 thus released from the shoulder 114 and, under the action of the spring 103, it is snapped to the right and, by reason of its engagement with a shoulder 107 on the collar-shifter 94, it moves the clutch-collar l to the right quicklyland resiliently presses it against the clutch-teeth on the gear 2 until they engage and thereby establish the driving connection. Conversely, when the table is traveling in the opposite direction, the shift-rod 93 is moved towards the left and the gravity link 118 (pivoted at 119) temporarily restrains the catch 101 from'being moved to the left until the bevel on the opposite catch 102 engages the bevel 120 on the gravity link 118 and raises it to release the catch 101. It will" be perceived that, by reason of this construction, the reverse lever 89 may be moved positively from either or tre1ne towards its other, but as soon as the clearance is taken up between the lever 89 and one or the other of the stop pins 143 of the prong 142 (which is loose on shaft 90) the reversing clutch will at once be snapped resiliently into place to effect a positive engagement the moment the clutchteeth come into registry. In this manner, the reversal is acconmlishrd within very close limits from any predetermined exact point on the table traverse.

' The automatic shock-absorbing table accelerator is arranged to function (when the low-"ear traverse lever .130 is not locked down by the seat 102) and it acts just before and immediately after the action of the 'reinto an engagement to eflect a reversal. The means for throwing the table into low gear preparatory to the reversal comprises a latch 109 pivoted to the dog 96 and having a contact surface 108 which travels in the path ofthe contact surface 111 of a plunger 112 spring-pressed by a spring 113. It will be A perceived that as the table advances, the

plunger 112 will be depressed and held down by the sloped surfaces 108 and; by the flat end 108 of the latch 109 and the ledge 96 of the dog ,96 and this throws the table in low gear, as will be explained. In the meantime, the reversing'lever is being moved and it operates the load-and-fire device only after the plunger 112 has been depressed and only while it remains depressed. Should it be desirable at any time to make the latch 109 ineffective, this may be done by withdrawing the finger-pin 110 from the lower l1ole.and looking it in the upper hole 96 Since the end 108 projects slightly below the ledge 96*, the latch 109 will be swung out of the way by the part 111 when the return takes place.

The effect of the plunger 112 is to swing the lever 121 (pivoted at 122) clockwise;

this being done by reason of the engagement of a pin 123 in the slotted end of said lever, as shown by Fig. 2. This lever also has a pin-and-slot connection 124 with the arm 125 affixed to shaft 126; thereby rotating said shaft counter-clockwise and swinging to the right a clutch-shifting arm 127 also secured to the shaft 126. The lower end of the arm 127 is slotted and receives a pin 128 projecting laterally from the clutch-shifter 129 which is slidably mounted on the rod 95 and which has a shoe engaging the clutch 1. Thus, each time the plunger 112 is depressed, the clutch-collar 1 will be moved to the right and will be disengaged from gear 9 and the motion will be transmitted only through the low-gear transmission. Should it be desired to accomplish the same result by hand, the aforesaid parts may be actuated through the hand-lever 130 which is arranged on the apron of the saddle immediately accessible to the user and which has a finger pin 131 whereby it may be engaged with the seat 132 if desired.

Means for dressing and truing the grinding-wheel may be provided but as this means forms no part of the present invention, it will suffice tosay that this may be done by mounting the usual diamond fixture on the work-carrier and causing it to move quite slowly across the face of the wheel. This slow traverse is obtained through the gears 8 and 8 by holding out of action the automatic speed-accelerator; which is done by pushing down the lever 130 and turning the eccentric pin-131 and pushing it into engagement with the seat 132 so as to hold down this lever, This lever, as shown byFig. 5

the front of the machine, and'the work-carrier will traverse only at its slow rate and that slow rate may also be varied by an appropriate shifting of the change-gears throughgthe hand-lever 80. With the ma chine so set, work of large diameter may likewise be ground or a IIIIIIOI finish may be ground.

It will thus be perceived that this motion W accelerator, considered as an entity is a compact sturdy unit well adapted to be combined with other elements to constitute various types of organized machines and, by following the combinationarrangements herein disclosed, the unit may be so-combined as to throw in and oflt of functional relation with the other elements so that the unit may be always available as the shock-absorbing motion accelerator, whenever it is desired to overcome the inertia or to absorb momentum of the parts to obviate shocks and jars.

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge, readily adapt it for various utilizations by retaining one or more of the features that, from the standpoint of the prior art, fairly constitute essential characteristics of either the generic or specific aspects of this invention and, therefore, such adaptations should be, and are intended to be, comprehended within the meaning and range of equivalency of the following claims:

Having thus revealed this invention, we

claim as 'new and desire to secure the f0l-' lowing combinations and elements, or equivalents .thereof, by Letters Patent of the United States:

1. A grinding-machine combining a workcarrier; a slow-motion transmission for ad vancing said work-carrier; a by-pass. transmission adapted to transmit motion more rapidly than said other transmission and to over-run the same withoutinterference; resilient means for enabling said by-pass trans mission gradually to speed up; and clutch mechanism for rendering either transmission operative.

2. A shock-absorbing reversing-mechanism for machine-tools combining a ratchet clutch; a slow-motion branch-line transmission operative to propel one member of said clutch; a fast-motion branch-line transmission operative to propel the other member of said clutch/to cause it to over-run said first-mentioned member; a motion accelerator combined with said fast-running branch line transmission; and clutch mechanism for rendering either the one or the other of said branch-line transmission operative, and a reverscr deriving motion through said ratchet-clutch.

3. A 1notion-accelerator for machine-tools combining a driving member; a driven member; an intervening element adapted to be rotated and also simultaneously translated, said element having a fixed ratio of rotation to one of said members and a variable ratio of rotation to the other member; and resilient means for progressively decreasing its ratio of rotation to said other member in proportion to its extent of translation.

4. A motion-accelerator for machine-tools combining a driving member and a driven member; an intervening member having a coarse-pitch threaded connection with one of said members and adapted to be simultancously rotated and translated relative thereto; resilient compression means for resisting said translation in proportion to the torque of the transmitted power; and a fixed ratio driving connection between said element and said other member.

5. A motion-accelerator combining a power transmitting member having coarse-pitch screw-threads; a telescoping element threaded thereto; a positive clutch adapted to cause said member and said element to rotate as a unit; and a spring tending to open said clutch but adapted to yield to permit said telescopic element to be translated by the torque of said screw threads to close said clutch.

6. A machine-tool combining a movable member having two trip contact-surfaces; a transmission for propelling said member embodying a gradually 'acting motion accelerator and a clutch fol-rendering said transmission inoperative; an element connected with said clutch and adapted to be shifted by said first contact-surface; and a part adapted to be actuated by said second contact-surface for causing said motion-ac celerator function.

7. A reversing mechanism for machinetools combining a traveling member: a reversing clutch: a driving unit embodying a clutch enabling it either to drive at a low rate or at a rate gradually increasing therefrom to a positlve higher ratio; a load-andfire mechanism for operating said reversing clutch; a trip element adapted to be moved by one of said contact-surfaces to disconnect said clutch and sinmltaneonsly to load said mechanism and then fire it to throw said clutch into its reversing position; and a part adapted to be tripped by said other contact surface to cause said unit to transmit motion at a slow rate before said mechanism fires and thereafter to cause said unit gradually to accelerate the rate of said member and ultimately propel it positively at the predetermined maximum rate.

8. A grinding-machine combining a workcarrier; a slow-motion transmission for advancing said work-carrier; a by-pass transmission adaptcd to transmit motion more rapidly than said other transmission and to over-run the same Without interference; resilient means for enabling said by-pass transmission graduall to speed up; clutch mechanism for rendering either transmission operative; and trip-mechanism operative by said work-carrier for controlling said clutchmeclianism.

9. A shock-absorbing reversing mechanism for machine-tools combining a ratchet clutch; a slow-motion branch-line transmis sion operative to propel one member of said clutch; a fast-motion branch-line transmission operative to propel the other member of said clutch to cause it to over-run said first-mentioned member; a motion accelerator combined with said fast-running branch line transmission; and clutch mechanism for rendering either the one or the other of said branch-line transmission operative; a reverser deriving motion through said ratchet-clutch; and automatic trip-means for periodically operating said clutch-mechanism and revcrscr. i

10. A sllock-absorbing-motion accelerator for machine. tools combining a ratchetclutch; a slow-motion transmission for driving the one member and a fast-motion transmission for driving the other member; tripmechanism for periodically rendering the one transmission eflective and the other ineffective, and conversely; and means for adjusting said trip-mechanism to regulate its periods of operation.

11. A motor-accelerator for machinetools combining a driving member; a driven member; an intervening element. adapted to be rotated and also simultaneously translated said element having a fixed ratio of rotation to one of said members and a veriable ratio of rotation to the other member; resilient, means for progressively decreasing its ratio of rotation to said other member in proportion to its extent of translation; and an adjustable trip-mechanism for determining the operation of said element,

12. A motion-accelerator for machinetools combining a driving member and a driven member: an intervening member having a coarse-pitch threaded connection with one of said members and adapted to be simultamaiusly rotated and translated relative thereto; resilient compression means for resisting said translation in proportion to the torque of the transmitted power; a fixed ratio driving connection between said element and said other member; and trip-mechanism for automatically rendering said member effective and ineffective to transmit motion positively.

13. A mo-tion-accelerator combining a power transmitting member having coarsepitch screw-threads; a telescoping element ltlO \ clutch; and trip-mechanism threaded thereto; a positive clutch adapted to cause said member and said element to rotate as a unit; a spring tending to open said clutch but adapted to yield to permit said telescopic element to be translated by the torque of said screw adapted alternately to impose torque upon and-relieve the torque upon said element.

14. A machine-tool combining a movable member having two trip contact-surfaces; a positive transmission; an ilnpo-sitive transmission for 1)1()1')(llll11 said member em bodying a gradual acting motion accelerator; a clutch for rendering said impositive lransmissi m inoperative; an element connected with said clutch and adapted to be shifted by said first contact-surface; and another clutch adapted to be actuated by said second contact-surface for reversing the direction of motion transmitted by each of said transmissions.

15. A reversing mechanism for machinetools combining a traveling member; a re vcrsing clutch; a driving unit embodying a clutch enabling it either to drive positively at a low rate or drive impositively at a rate gradually increasing therefrom to a positive drive at a higher ratio; a load-and-fire mechanism for operating said reversing .clutch; a trip element adapted to be moved by one of said contact-surfaces to disconnect said clutch and simultaneously to load said mechanism and then fire it to throw said clutch into its reversin position; and a part adapted'to be tripped by said other contact surface to cause said unit to transmit motion positively at a slow rate before said mechanism fires and thereafter im ositively and to cause said unit gradual y to acceleratethe rate of said member and ultimately propel it positively at the predetermined maximum rate.

v 16. A motion-accelerator for machinetools combining a driving member; a driven member; an intervening element adapted to be rotated and also simultaneously translated, said element having a constant ratio of rotation to one of said members and a variable ratio of rotation to the other member; resilient means for progressively decreasing its ratio of rotation to said other member in proportion to its extent of translation; and a positive clutch automatically operative to render constant said variable rate.

17. A motion-accelerator for machinetools combining adriving member and a driven member; an intervening member having a coarse-pitch threaded connection with one of said members and adapted through said connection to be simultaneously rotated and translated relative thereto resilient compression means for resisting said translation in proportion to the torque threads to close said of the transmitted power; and a fixed ratio driving connection between said elementand said other member adapted to become operative when a predetermined torque has been attained.

1.8. A motion-accelerator combining a power transmitting member having coarsepitch screw-threads; a telescoping element threaded thereto; a second member splined to said element; a positive clutch adapted to cause said member and said two elements to rotate as a unit: and a spring tending to open said clutch but adapted to yield under a predetermined torque to permitjsaid telescopic element to be translated by the torque of said screw threads to close said clutch.

19. A motionaccelerator for machinetools combining a driving member; a driven member; an intervening elementadapted to be rotated and also simultaneously translated, said element having a fixed ratio of rotation to one of said members and a variable ratio of rotation to the other member: and an expansile coiled spring and adapted to be gradually compressed by the torque of the transmitted motion for progressively decreasing its ratio of rotation to said other member in proportion to its extent of translation.

20. A motion-accelerator for machinetools combining a driving member and a.

driven member; a tubular intervening member having a coarse-pitch threaded connection with one of said members and adapted to be simultaneously rotated and translated relative thereto; resilient compression means housed within said tubular member for resisting said translation in proportion to the torque of the transmitted power; and a fixed ratio driving connection between said element and said other member.

21. A motion-accelerator combining a power transmitting member having coarsepitch screw-threads; a telescoping element threaded thereto; a positive clutch adapted to cause said member and said element to rotate as a unit; and a spring housed within said element and tending to shift it to open said clutch but adapted to yield to permit said telescopic element to be translated in an opposite direction by the torque of said screw threads to close said clutch.

22. A grinding-machine combining a work-carrier; a positive slow-motion transmission for advancing said work-carrier; an 'impositive by-pass transmission adapted to transmit motion more rapidly than said other transmission and to over-run the same without interference; resilient means for enabling said by-pass transmission gradually to speed up; and a'hand lever for disconnecting said impositive transmission and rendering said positive transmission alone adapted to transmit motion.

23. A shock-absorbing reversing mechanism for machine-tools combining a ratchetclutch; a slow-motion branch line transmis sion operative topropel one member of said clutch; a fast-motion branch-line transmission operative to propel the other member of said clutch tocause it to over-run said firstlever for preventing said clutch-mechanism from automatically causing said vslowmotlon transmission to function.

24. A shock-absorbing-motion accelerator for machine tools combining a ratchetclutch; a slow-motion transmission for driving the one member and a fast-motion transmission for '(lllVlng the other member;

means for alternately rendering the onetransmission effective and the other ineifective; and a hand-lever adapted to be set to cause the slow-motion transmission alone to operate.

transmission inoperative; an element connected with said clutch and adapted to be shifted by said first contact-surface for causing said motion-accelerator to function; and manual means for rendering said part inoperative.

26. A reversing mechanism for machinetools combining a traveling member; a reversing clutch; a driving unit embodying a clutch enabling it either to drive at a low rate or at a rate gradually increasing therefrom to a positive higher ratio; a load-andfire mechanism for operating said reversing clutch; a trip element adapted to be moved by one of said contact-surfaces to load said mechanism and then fire it to throw said clutch into its reversing position; a part adapted to be tripped by said other contact surface to cause said unit to transmit motion at a slow rate before said mechanism fires and thereafter to caua said unit gradually to accelerate the rate of said member and ultimately propel it positively at the predetermined maximum rate; and a handlever for holding said clutch in its low driving position. i

In witness whereof, we hereunto subscribe our names.

SOL EINSTEIN.- HERMAN R. ISLER. 

